The present invention relates to a slip anchor for a seat belt device, more particularly, to a slip anchor for a seat belt device which is fixed to an upper portion of a pillar or the like of a vehicle to slidably guide a webbing unwound from a retractor of the seat belt device in a direction which an occupant can easily wear the webbing.
As well known in the art, a seat belt device mounted on a seat or the like of a vehicle restrains an occupant's body from sudden movement by deceleration and impact occurred during a crash to secure the occupant.
Such a seat belt device comprises a webbing (hereinafter, we call a webbing as a woven belt made of a normal fabric which has approximately a 50 mm width and is provided by Japanese Industrial Standard in this specification), a retractor (hereinafter, ELR: Emergency Locking Retractor is designated instead of the retractor) for winding the webbing inside thereof by a biasing force of a spring and for locking the webbing from unwinding only when an impact is applied by a crash to restrain the occupant from moving, a buckle disposed at a proper position so that the webbing fits to the occupant's body, a tongue as a connection member between the buckle and webbing, anchors for fixing the webbing to a predetermined position in the vehicle by a fixing portion such as a bolt, and so on.
The anchors are classified into a fixing anchor and a slip anchor. The fixing anchor is used for fixing the end of the webbing of a lap belt at a position near the floor of the vehicle. The slip anchor is mounted on the upper position of the pillar of the vehicle by a fixing bolt or the like so as to pivot on the fixing bolt in a predetermined direction.
The slip anchor changes the extending direction of the webbing which is unwound upwardly along the pillar from the ELR to a downward direction. The ELR is disposed in the pillar and positioned substantially at the side of the occupant. Thereby, the webbing is guided by the slip anchor as a shoulder belt to stretch over at the front of the occupant's chest when the seat belt is worn. In addition, the slip anchor guides the webbing to be accommodated in the retractor toward the ELR when the seat belt is not worn.
Further, the slip anchor works as a supporting point when the shoulder belt locked from unwinding restrains the occupant from the forward movement, and bears a tensile force from the shoulder belt at a crash. The slip anchor has a guide portion for smoothly guiding the webbing so that the webbing can freely move to and fro and a fixing portion fixed to a frame or the like of the vehicle so as to withstand the force at a crash. In addition, the slip anchor is structured not to be deformed itself when the force is applied.
FIG. 1 (a) and FIG. 1 (b) show an example of a conventional slip anchor. The slip anchor 50 comprises a steel plate 51 made by punching from a steel sheet having a predetermined thickness and a resin guide portion 53 formed by a resin mold using a part of the steel plate 51 as an insert metal thereof.
The steel plate 51 consists of a mounting portion having a fixing hole 51a and a guide portion having a guide slot 52. A portion contacting the webbing of the resin guide portion 53 is molded in a rough circular arc shape (See FIG. 1 (b)). Thereby, the webbing W inserted into the guide slot 52 formed in an elongated hole shape slides smoothly to be guided.
The guide slot 52 has escape areas 52a formed on the both ends thereof. The escape areas 52a prevent the webbing W from twisting and prevent the edge of the webbing from warping when the webbing W is guided through the slip anchor.
The bolt head is covered by a resin cover C for the beauty and the safety.
The slip anchor of such a type shown in FIG. 1 (a) is made by an insert-molding process or the like. That is, the steel plate 51 is buried previously as the insert metal in a predetermined position in a mold and the resin is then injected into the mold. It is preferred to smoothly share the force applied to the slip anchor between the steel plate 51 and the resin portion at a crash or the like.
However, when the steel plate has little rigidity, the steel plate is deformed when a force is applied rapidly to it at a crash or the like so that the resin member can not follow the deformation of the steel plate and is then cracked.
For solving the problem, it is possible to increase the thickness of the plate for increasing the rigidity thereof. However, as the thickness is increased, each interval between the steel plates to be punched should be enlarged satisfactorily when the steel plates are punched from a steel sheet material. Thereby, there is waste of the material on blanking, so that the cost of parts is increased as increasing the thickness of the material.
For holding back the increase of the weight of the vehicle as a whole, it is an important object to lighten the weights of parts for vehicle. In the slip anchor described above, the plate needs to be thickened or expanded in size for increasing the rigidity. As the result of this, the weight of parts is increased and this is a fault of vehicle parts.